scsi: iscsi: Stop using the SCSI pointer

Instead of storing the iSCSI task pointer and the session age in the SCSI
pointer, use command-private variables. This patch prepares for removal of
the SCSI pointer from struct scsi_cmnd.

The list of iSCSI drivers has been obtained as follows:
$ git grep -lw iscsi_host_alloc
drivers/infiniband/ulp/iser/iscsi_iser.c
drivers/scsi/be2iscsi/be_main.c
drivers/scsi/bnx2i/bnx2i_iscsi.c
drivers/scsi/cxgbi/libcxgbi.c
drivers/scsi/iscsi_tcp.c
drivers/scsi/libiscsi.c
drivers/scsi/qedi/qedi_main.c
drivers/scsi/qla4xxx/ql4_os.c
include/scsi/libiscsi.h

Note: it is not clear to me how the qla4xxx driver can work without this
patch since it uses the scsi_cmnd::SCp.ptr member for two different
purposes:
- The qla4xxx driver uses this member to store a struct srb pointer.
- libiscsi uses this member to store a struct iscsi_task pointer.

Reviewed-by: Lee Duncan <[e-mail]>
Reviewed-by: Hannes Reinecke <[e-mail]>
Reviewed-by: Himanshu Madhani <[e-mail]>
Cc: Chris Leech <[e-mail]>
Cc: Sagi Grimberg <[e-mail]>
Cc: Nilesh Javali <[e-mail]>
Cc: Manish Rangankar <[e-mail]>
Cc: Karen Xie <[e-mail]>
Cc: Ketan Mukadam <[e-mail]>
Signed-off-by: Bart Van Assche <[e-mail]>

iscsi

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/infiniband/ulp/iser/iscsi_iser.c

···
 	.proc_name              = "iscsi_iser",
 	.this_id                = -1,
 	.track_queue_depth	= 1,
+	.cmd_size		= sizeof(struct iscsi_cmd),
 };
 
 static struct iscsi_transport iscsi_iser_transport = {

drivers/scsi/be2iscsi/be_main.c

···
 
 static int beiscsi_eh_abort(struct scsi_cmnd *sc)
 {
-	struct iscsi_task *abrt_task = (struct iscsi_task *)sc->SCp.ptr;
+	struct iscsi_task *abrt_task = iscsi_cmd(sc)->task;
 	struct iscsi_cls_session *cls_session;
 	struct beiscsi_io_task *abrt_io_task;
 	struct beiscsi_conn *beiscsi_conn;
···
 	.cmd_per_lun = BEISCSI_CMD_PER_LUN,
 	.vendor_id = SCSI_NL_VID_TYPE_PCI | BE_VENDOR_ID,
 	.track_queue_depth = 1,
+	.cmd_size = sizeof(struct iscsi_cmd),
 };
 
 static struct scsi_transport_template *beiscsi_scsi_transport;

drivers/scsi/bnx2i/bnx2i_iscsi.c

···
 	.sg_tablesize		= ISCSI_MAX_BDS_PER_CMD,
 	.shost_groups		= bnx2i_dev_groups,
 	.track_queue_depth	= 1,
+	.cmd_size		= sizeof(struct iscsi_cmd),
 };
 
 struct iscsi_transport bnx2i_iscsi_transport = {

drivers/scsi/cxgbi/cxgb3i/cxgb3i.c

···
 	.dma_boundary	= PAGE_SIZE - 1,
 	.this_id	= -1,
 	.track_queue_depth = 1,
+	.cmd_size	= sizeof(struct iscsi_cmd),
 };
 
 static struct iscsi_transport cxgb3i_iscsi_transport = {

drivers/scsi/cxgbi/cxgb4i/cxgb4i.c

···
 	.dma_boundary	= PAGE_SIZE - 1,
 	.this_id	= -1,
 	.track_queue_depth = 1,
+	.cmd_size	= sizeof(struct iscsi_cmd),
 };
 
 static struct iscsi_transport cxgb4i_iscsi_transport = {

drivers/scsi/iscsi_tcp.c

···
 	.proc_name		= "iscsi_tcp",
 	.this_id		= -1,
 	.track_queue_depth	= 1,
+	.cmd_size		= sizeof(struct iscsi_cmd),
 };
 
 static struct iscsi_transport iscsi_sw_tcp_transport = {

drivers/scsi/libiscsi.c

···
 
 	if (sc) {
 		/* SCSI eh reuses commands to verify us */
-		sc->SCp.ptr = NULL;
+		iscsi_cmd(sc)->task = NULL;
 		/*
 		 * queue command may call this to free the task, so
 		 * it will decide how to return sc to scsi-ml.
···
 	if (!task || !task->sc)
 		return NULL;
 
-	if (task->sc->SCp.phase != conn->session->age) {
+	if (iscsi_cmd(task->sc)->age != conn->session->age) {
 		iscsi_session_printk(KERN_ERR, conn->session,
 				  "task's session age %d, expected %d\n",
-				  task->sc->SCp.phase, conn->session->age);
+				  iscsi_cmd(task->sc)->age, conn->session->age);
 		return NULL;
 	}
 
···
 			 (void *) &task, sizeof(void *)))
 		return NULL;
 
-	sc->SCp.phase = conn->session->age;
-	sc->SCp.ptr = (char *) task;
+	iscsi_cmd(sc)->age = conn->session->age;
+	iscsi_cmd(sc)->task = task;
 
 	refcount_set(&task->refcount, 1);
 	task->state = ISCSI_TASK_PENDING;
···
 	struct iscsi_task *task = NULL;
 
 	sc->result = 0;
-	sc->SCp.ptr = NULL;
+	iscsi_cmd(sc)->task = NULL;
 
 	ihost = shost_priv(host);
 
···
 
 	spin_lock_bh(&session->frwd_lock);
 	spin_lock(&session->back_lock);
-	task = (struct iscsi_task *)sc->SCp.ptr;
+	task = iscsi_cmd(sc)->task;
 	if (!task) {
 		/*
 		 * Raced with completion. Blk layer has taken ownership
···
 	 * if session was ISCSI_STATE_IN_RECOVERY then we may not have
 	 * got the command.
 	 */
-	if (!sc->SCp.ptr) {
+	if (!iscsi_cmd(sc)->task) {
 		ISCSI_DBG_EH(session, "sc never reached iscsi layer or "
 				      "it completed.\n");
 		spin_unlock_bh(&session->frwd_lock);
···
 	 * then let the host reset code handle this
 	 */
 	if (!session->leadconn || session->state != ISCSI_STATE_LOGGED_IN ||
-	    sc->SCp.phase != session->age) {
+	    iscsi_cmd(sc)->age != session->age) {
 		spin_unlock_bh(&session->frwd_lock);
 		mutex_unlock(&session->eh_mutex);
 		ISCSI_DBG_EH(session, "failing abort due to dropped "
···
 	}
 
 	spin_lock(&session->back_lock);
-	task = (struct iscsi_task *)sc->SCp.ptr;
+	task = iscsi_cmd(sc)->task;
 	if (!task || !task->sc) {
 		/* task completed before time out */
 		ISCSI_DBG_EH(session, "sc completed while abort in progress\n");

drivers/scsi/qedi/qedi_fw.c

···
 		goto error;
 	}
 
-	if (!sc_cmd->SCp.ptr) {
+	if (!iscsi_cmd(sc_cmd)->task) {
 		QEDI_WARN(&qedi->dbg_ctx,
-			  "SCp.ptr is NULL, returned in another context.\n");
+			  "NULL task pointer, returned in another context.\n");
 		goto error;
 	}
 

drivers/scsi/qedi/qedi_iscsi.c

···
 	.dma_boundary = QEDI_HW_DMA_BOUNDARY,
 	.cmd_per_lun = 128,
 	.shost_groups = qedi_shost_groups,
+	.cmd_size = sizeof(struct iscsi_cmd),
 };
 
 static void qedi_conn_free_login_resources(struct qedi_ctx *qedi,

drivers/scsi/qla4xxx/ql4_def.h

···
 #define IDC_COMP_TOV			5
 #define LINK_UP_COMP_TOV		30
 
-#define CMD_SP(Cmnd)			((Cmnd)->SCp.ptr)
+/*
+ * Note: the data structure below does not have a struct iscsi_cmd member since
+ * the qla4xxx driver does not use libiscsi for SCSI I/O.
+ */
+struct qla4xxx_cmd_priv {
+	struct srb *srb;
+};
+
+static inline struct qla4xxx_cmd_priv *qla4xxx_cmd_priv(struct scsi_cmnd *cmd)
+{
+	return scsi_cmd_priv(cmd);
+}
 
 /*
- * SCSI Request Block structure	 (srb)	that is placed
- * on cmd->SCp location of every I/O	 [We have 22 bytes available]
+ * SCSI Request Block structure (srb) that is associated with each scsi_cmnd.
  */
 struct srb {
 	struct list_head list;	/* (8)	 */

drivers/scsi/qla4xxx/ql4_os.c

···
 	.name			= DRIVER_NAME,
 	.proc_name		= DRIVER_NAME,
 	.queuecommand		= qla4xxx_queuecommand,
+	.cmd_size		= sizeof(struct qla4xxx_cmd_priv),
 
 	.eh_abort_handler	= qla4xxx_eh_abort,
 	.eh_device_reset_handler = qla4xxx_eh_device_reset,
···
 	srb->ddb = ddb_entry;
 	srb->cmd = cmd;
 	srb->flags = 0;
-	CMD_SP(cmd) = (void *)srb;
+	qla4xxx_cmd_priv(cmd)->srb = srb;
 
 	return srb;
 }
···
 		scsi_dma_unmap(cmd);
 		srb->flags &= ~SRB_DMA_VALID;
 	}
-	CMD_SP(cmd) = NULL;
+	qla4xxx_cmd_priv(cmd)->srb = NULL;
 }
 
 void qla4xxx_srb_compl(struct kref *ref)
···
 			 * the scsi/block layer is going to prevent
 			 * the tag from being released.
 			 */
-			if (cmd != NULL && CMD_SP(cmd))
+			if (cmd != NULL && qla4xxx_cmd_priv(cmd)->srb)
 				break;
 		}
 		spin_unlock_irqrestore(&ha->hardware_lock, flags);
···
 	if (!cmd)
 		return srb;
 
-	srb = (struct srb *)CMD_SP(cmd);
+	srb = qla4xxx_cmd_priv(cmd)->srb;
 	if (!srb)
 		return srb;
 
···
 
 	do {
 		/* Checking to see if its returned to OS */
-		rp = (struct srb *) CMD_SP(cmd);
+		rp = qla4xxx_cmd_priv(cmd)->srb;
 		if (rp == NULL) {
 			done++;
 			break;
···
 	}
 
 	spin_lock_irqsave(&ha->hardware_lock, flags);
-	srb = (struct srb *) CMD_SP(cmd);
+	srb = qla4xxx_cmd_priv(cmd)->srb;
 	if (!srb) {
 		spin_unlock_irqrestore(&ha->hardware_lock, flags);
 		ql4_printk(KERN_INFO, ha, "scsi%ld:%d:%llu: Specified command has already completed.\n",

include/scsi/libiscsi.h

···
 #include <linux/refcount.h>
 #include <scsi/iscsi_proto.h>
 #include <scsi/iscsi_if.h>
+#include <scsi/scsi_cmnd.h>
 #include <scsi/scsi_transport_iscsi.h>
 
 struct scsi_transport_template;
···
 	return task->state == ISCSI_TASK_COMPLETED ||
 	       task->state == ISCSI_TASK_ABRT_TMF ||
 	       task->state == ISCSI_TASK_ABRT_SESS_RECOV;
+}
+
+/* Private data associated with struct scsi_cmnd. */
+struct iscsi_cmd {
+	struct iscsi_task	*task;
+	int			age;
+};
+
+static inline struct iscsi_cmd *iscsi_cmd(struct scsi_cmnd *cmd)
+{
+	return scsi_cmd_priv(cmd);
 }
 
 /* Connection's states */